1. The Field of the Invention
This invention relates to a lathe having a lathe bed, a cutting station provided on the lathe bed and at which a cutting tool can be mounted, a guide mounted on the lathe bed and defining a guide path for guiding relative movement between a workpiece and the cutting tool, and drive means for relatively moving the workpiece and the cutting tool to engagement with each other.
2. The Relevant Technology
In known designs of lathe, it is usual to provide a so-called xe2x80x9cremovable gap-piecexe2x80x9d, and which (when removed) temporarily gives an increased xe2x80x9cgap-swingxe2x80x9d capacity for a short distance in front of the usual faceplate which holds the workpiece. However, with existing designs, the presumed requirement of lathe operators for a removable gap-piece facility presently imposes a number of technical drawbacks, which can include (a) loss of overall accuracy (b) reduction of rigidity and (c) undesirable wear characteristics of the lathe.
The present invention therefore seeks, in one aspect, to provide an improved design of lathe which allows for elimination of a traditional removable gap piece, while at the same time seeking to provide improved overall accuracy in operation, rigidity and enhanced wear characteristics of the lathe.
According to one aspect of the invention there is provided a lathe having a lathe bed on which is mounted:
a) a cutting station at which a cutting tool can be mounted;
b) a guide defining a guide path for guiding relative feeding movement between a workpiece holder and the cutting tool; and
c) drive means for relatively moving the workpiece and the cutting tool to engagement with each other:
in which the guide comprises three parallel guide elements which are spaced apart from each other and relative to the center line of the workpiece holder such that a permanent gap or cavity is defined in the lathe bed structure to provide a gap-swing facility and substantially without loss of guide-way support.
Preferably, the three parallel guide elements comprise a main front guideway, a tailstock bed-way, and a rear anti-roll guideway.
The drive means may take the form of a usual lead screw arrangement.
The cutting tool is preferably carried by a travelling assembly movable along the guide elements, and including two front carriages slidable along the main front guideway, and a further carriage unit slidable along the rear anti-roll guideway.
The preferred provision of a three-point linear guideway configuration (two carriages slidable along the front main guideway and one preferably less heavily pre-loaded carriage unit sliding on the rear anti-roll guideway) allows for some geometric misalignment, thus further improving overall slide-way accuracy.
The geometry of the arrangement of the guide elements, in relation to the center line of the workpiece holder (main spindle center line) is arranged, as indicated above, to provide a permanent cavity or gap in the lathe bed, and to allow for appropriate extra xe2x80x9cgap-swingxe2x80x9d which may be required, without the usual loss of slide-way support which naturally occurs when a traditional gap piece is removed in known designs of lathe provided with this facility.
Further advantages of the embodiment of the invention are that the loss of accuracy, often introduced by non-perfect refitting of a traditional gap piece (after removal for xe2x80x9cswing-in gap workxe2x80x9d) is eliminated. In addition, the length limit imposed by a gap piece (to the desirably long and narrow) main guideway may also be eliminated, thus giving opportunity to increase this length and consequently provide improved slideway accuracy, rigidity and enhanced wear properties.
According to a further aspect of the invention there is provided a lathe having a lathe bed on which is mounted:
a) a cutting station at which a cutting tool can be mounted;
b) a guide defining a guide path for guiding feeding movement of the cutting tool relative to a workpiece holder; and
c) drive means for advancing the cutting tool into engagement with a workpiece when mounted on said holder;
in which the lathe excludes provision of a removable gap piece, and in which said guide comprises three parallel guide elements which are spaced apart from each other and relative to the center line of the workpiece holder that a permanent gap or cavity is defined in the lathe bed to provide a gap-swing facility and substantially without loss of guide-way support for the movement of the cutting tool.